Democratic leaders conferred on Friday about new and unexpected prospects for pushing their agenda thanks to the defection of a key Republican in the Senate that will shift power in the chamber to their party.

President Bush tried to play down the enormity of the change and signaled confidence in top aides who critics say failed to stop the defection of moderate Sen. James Jeffords of Vermont, who objected to Bush's conservative trend.

Yet the future of Bush's legislative agenda, including tackling energy shortages, education and health reform, promoting more conservative judicial appointments and reshaping national security with a missile defense system, was now in question.

Jeffords' defection, announced on Thursday, will change the balance of power in the Senate to 50 Democrats, 49 Republicans and one independent. Republicans control the House of Representatives, 221-210, with two independents and two vacant seats.

"The dynamics on the Hill change immediately," said Kim Wallace, chief political analyst at the Lehman Brothers investment bank. "You return to shared power and have, at best, grudging partisan negotiations or return to an era of gridlock when you get nothing done.

"This can't be viewed as good for President Bush," Wallace said. "Yet Democrats could be at risk if there is more gridlock and the public blames them for it."

Senate Democratic leader Tom Daschle, in line to become the chamber's new majority leader, met with House Democratic leader Richard Gephardt as shell-shocked Republicans regrouped.

Daschle of South Dakota has said the first new piece of legislation he will bring to the floor when Democrats take control will be a long-stalled measure to establish a patients' bill of rights.

Assistant Senate Republican Leader Don Nickles reiterated on Friday he may try to muster a vote-blocking filibuster against the measure, maintaining it would raise health costs and force some companies to drop coverage of workers.

"I'm a reluctant warrior," said Nickles of Oklahoma. "I want to pass a patients' bill of rights," but not this one.

An aide said Daschle would decide the lineup of other bills after Congress returns from its Memorial Day recess on June 4 -- WASHINGTON (Reuters)